Based on their circuit composition, crystal oscillators are classified into active and passive types.
Passive crystal oscillator refers to a crystal component.
Passive crystal oscillators require clock circuits to generate oscillation signals and cannot oscillate independently, making the term "passive crystal oscillator" inaccurate. These devices only have two input/output pins and lack positive/negative polarity terminals.
The active crystal oscillator is an Oscillator (oscillator).
An active crystal oscillator is a complete resonant oscillator that requires a power supply to operate. It typically features four pins: an OE tri-state function control pin, a GND ground pin, an OUT output pin, and a power input pin, with positive and negative polarity distinctions.
Definition of Quartz Crystal Oscillator
A quartz crystal resonator (also known as crystal or crystal oscillator) is a piezoelectric device utilizing the piezoelectric effect of quartz crystals (crystalline silicon dioxide). Its fundamental structure involves cutting thin slices (referred to as wafers, which may be square, rectangular, or circular) from a quartz crystal at specific orientation angles. Silver layers are applied to two corresponding surfaces as electrodes, with each electrode connected to a lead wire via soldering to corresponding pins. The assembly is then encapsulated in a protective housing. While most products feature metal casings, alternative packaging options include glass, ceramic, or plastic materials.
Based on their functions and implementation technologies, crystal oscillators are classified into three types: temperature-compensated crystal oscillator (TCXO), voltage-controlled crystal oscillator (VCXO), and constant temperature crystal oscillator (OCXO).
Temperature Compensation Crystal Oscillator (TCXO)
This quartz crystal oscillator reduces frequency variation caused by ambient temperature changes through an additional temperature compensation circuit. The compensation methods for frequency temperature drift in quartz crystal oscillators primarily include direct compensation and indirect compensation. Applications include IoT systems, radar systems, and base stations. Frequency range: selectable from 15MHz to 2100MHz.
Voltage-Controlled Crystal Oscillator (VCXO)
It is a quartz crystal oscillator that allows variable or modulable oscillation frequency through external control voltage application. In typical VCXO systems, the frequency of the quartz crystal oscillator is typically "tuned" by adjusting the capacitance of varactor diodes via tuning voltage. Key applications include testing equipment, cellular base stations, and lidar systems. Frequency range: selectable from 15MHz to 2100MHz.
Temperature-stable crystal oscillator (OCXO)
An OCXO (Optical Crystal Oscillator) is a crystal oscillator that maintains a constant temperature for the crystal oscillator or quartz crystal oscillator using a constant temperature bath, thereby minimizing frequency variations in the oscillator output caused by ambient temperature changes. OCXOs are primarily used in wireless communications, satellite navigation, power systems, aerospace equipment, and other applications. Frequency range: selectable from 5 MHz to 200 MHz.
